Re: ssh inside a loop problem

[Bob Proulx]

caudio wrote:
> Hi everybody!  I have recently had a problem trying to make an ssh
> runn inside a loop.

Your question is really not about a bug in bash.  It would be more
appropriate for a general shell script discussion list.  It is
somewhat off-topic here.

Having said that, I can't resist commenting regardless.

> for s in $(cat $SERVER_FILE);

Search the web for "useless use of cat".

>       do
>       ssh $s "

Because your argument is a double-quoted string all $var variables
will be expanded on the local machine and not on the remote machine.

> PATH=$PATH:/usr/local/bin:/usr/local/sbin:/usr/sbin:/usr/lbin:/usr/local/etc; 
>         
This will be the $PATH on the local machine because of this.

>       for i in $(cat $USERS_FILE);

This will be the $USERS_FILE on the local machine, which is what you
want, I think.

>               do 
>               echo $i >> $HOME/line ||touch $HOME/line

This will be the $i on the local machine, which is *not* what you
want.  You will need to quote the $ there so that it gets expanded on
the remote machine.

And so on.

>               line=$(sed -e 's/_/ /g' $HOME/line)
>               NetworkId=$(echo "$line");
>               rm -r $HOME/line

Is the -r needed there?  Safer without it.

I think there is a lot of unnecessary work being done there but I
don't have the brain cells at the moment to analyze it further and
will simply note that this bothers me.

>               sudo userdel -r $NetworkId  
>               echo "All the task on Server:$s has been completed :D"

Where is 's' set?

>               done
>               
>               exit "
> done

The technique I like better is to cat the script into the remote
machine.  Consider something like this:

  s=somethinghere
  ssh host.example.com sh <<EOF
PATH=\$PATH:/usr/local/bin:/usr/local/sbin:/usr/sbin:/usr/lbin:/usr/local/etc;
for i in $(<$USERS_FILE); do 
  echo \$i >> \$HOME/line || touch \$HOME/line
  line=\$(sed -e 's/_/ /g' \$HOME/line)
  NetworkId=\$(echo "$line");
  rm \$HOME/line
  sudo userdel -r \$NetworkId  
  echo "All the task on Server:$s has been completed :D"
done
exit 0
EOF

Or like this:

PATH=$PATH:/usr/local/bin:/usr/local/sbin:/usr/sbin:/usr/lbin:/usr/local/etc;
for i in $(<$USERS_FILE); do 
  echo $i >> $HOME/line || touch $HOME/line
  line=$(sed -e 's/_/ /g' $HOME/line)
  NetworkId=$(echo "$line");
  rm $HOME/line
  ssh host.example.com sh <<EOF
  sudo userdel -r $NetworkId  
EOF
  echo "All the task on Server:$s has been completed :D"
done
exit 0

I did not test any of this.

I assume by your use here that you have sudo configured to not ask for
a password?  Otherwise this will need adjustment.

Good luck!

Bob